Fernando Alonso believes the Ferrari updates "seem to work" during Friday practice for the United States Grand Prix but still predicts a difficult qualifying session.

While championship rival Sebastian Vettel dominated practice, Alonso was third quickest in FP2 but over three quarters of a second slower than Vettel. Alonso said he didn't expect to qualify in third place because McLaren and Lotus could be quicker on Saturday but he was still confident he could take points from Vettel come the race.

"I think the updates seem to work," Alonso said. "We're still analysing all the data from today but the first impression is that it's all going good so I'm happy but obviously if we introduce a little step at every race the others are doing the same so we keep the gap more or less consistent.

"Starting third would be fantastic but we were third on many Fridays but then on Saturday the McLarens, Lotus etc they seem to use their potential as well. On Friday maybe they hide something so it's possible that we'll have a tough qualifying but we were seventh and ninth in Abu Dhabi and we scored three points more than Vettel so we are better than seventh. I think we can score more points than him."

Alonso added that Vettel's advantage during Friday had not come as a surprise to Ferrari.

"No surprises for us, they are the quickest out there, they have the fastest package, they do first and second in all the practice, first and second in all qualifyings and if everything goes normal first and second in the race. But in the race but sometimes everything is not going normal; we put more pressure on them on Sundays. We will take our opportunities, we will fight every lap in the race and we know the strong point of them is the speed of the package. They are very quick. Our strong points are the united team, a very strong team, the ability of our car and we try to use each of our strong points."